An FCoE technique is a technique that operates a Fibre Channel (FC) protocol family based on Ethernet. In an FCoE system, an Ethernet node (ENode) such as a server, a storage device and the like, is connected to an Ethernet interface of an FCoE Forwarder (FCF), which in turn is connected to an FC network via an FC interface of the FCF.
Specifically, referring to FIG. 1, between each ENode and an FCF connected thereto, there is not only a physical link between Ethernet interfaces in an Ethernet layer, but also a virtual logic link between a Virtual Node (VN) port and a Virtual Fibre Channel (VFC) port in an FC layer, which is called a virtual link for short, namely, a logic connection formed by the VN port→the Ethernet interface of the ENode→the Ethernet interface of the FCF→the VFC port.
Referring to FIG. 2, a process of virtual link discovery between an ENode and an FCF may be realized through FCoE Initialization Protocol (FIP) messages, which specifically comprises the following operations.
Block 201: the ENode sends, via its VN port, an FIP Discovery Solicitation message to a VFC port of an FCF that has the highest priority or whose forwarder name has the largest value among all of the FCFs.
Block 202: the FCF checks an address mode of the ENode.
Block 203: the FCF returns, via its VFC port, an FIP Discovery Advertisement message to the VN port of the ENode after the address mode check of the ENode is passed.
Block 204: the ENode checks a maximum size (MAX size) of the Discovery Advertisement message and obtains a physical (MAC) address of the FCF.
Block 205: the ENode sends, via its VN port, a Virtual Link Instantiation Request message carrying a Fabric Login (FLOGI) message to the VFC port of the FCF after the MAX size check is passed.
Block 206: the FCF activates the VFC port according to the FLOGI message carried in the Virtual Link Instantiation Request message.
Block 207: the FCF determines whether a login of the VN port of the ENode is allowed, and replies a Virtual Link Instantiation Reply message carrying a login response (LS_ACC) message to the VN port of the ENode if the login of the VN port of the ENode is allowed.
Block 208: the ENode activates the VN port that has logged into the VFC port of the FCF according to the LS_ACC message carried in the Virtual Link Instantiation Reply message, so that a virtual link between this VN port and the VFC port of the FCF is established.
So far, the process of virtual link discovery ends.
Thus, in addition to having such advantages as I/O integration and network uniformity, the FCoE system based on virtual links can change an FC network topology substantively by arbitrarily establishing different virtual links between FCFs and ENodes.
Referring to FIG. 3, suppose that there are two FCFs and four ENodes, virtual links (as shown by solid lines in FIG. 3) are established between each of ENodes 1-4 and FCF1 according to the process shown in FIG. 2, and ENodes 1-4 access an FC network through the virtual links to FCF1. When a fault occurs in FCF1, ENodes 1-4 may switch to F CF2 serving as a backup and establish virtual links to FCF2 (as shown by dashed lines in FIG. 3), and may access the FC network again through the virtual links to FCF2, so that link backup for the FC network topology is realized and hence network reliability is improved.
However, in the existing networking ways by which the link backup for the FC network topology is realized, all the ENodes will access the same FCF that has the highest priority or whose forwarder name has the largest value upon discovery of a virtual link according to the process shown in FIG. 2. That is, in block 201, all the ENodes may only send the Discovery Solicitation messages to the same specified FCF that has the highest priority or whose forwarder name has the largest value according to such predefined information as the priority of the FCF or the forwarder name. As a result, all the ENodes access the same FCF, such as FCF1 in FIG. 3, while other FCFs serving as backups, such as FCF2 in FIG. 3, may remain in an idle state for a long time.
In this case, the FCF that all the ENodes access may have message congestion, while the resources of the FCFs serving as backups are. Furthermore, during the switching to the backup, each of the ENodes has to perform the process of virtual link discovery as shown in FIG. 2, so that an efficiency of switching the virtual links is low.